1. Field of the Invention
The present invention relates to a data carrier and a data carrier system, and more particularly, to a technique preferable for being used for performing both RF communication and contact serial communication between a data carrier and a reader/writer apparatus.
2. Description of the Related Art
Conventionally, a data carrier system has been put to practical use in various fields which is configured by a data carrier and a reader/writer apparatus and in which data is given and received between the data carrier and the reader/writer apparatus. In such a data carrier system, the data carrier obtains operating power by receiving the alternating magnetic field at the carrier frequency provided by the reader/writer apparatus via an antenna circuit, with an antenna included in the data carrier.
An inquiry signal including a command or data is transmitted by modulating the magnetic field provided by the reader/writer apparatus, and the data carrier demodulates it to receive the command or the data transmitted from the reader/writer apparatus.
On the other hand, in the case of transmitting data from the data carrier to the reader/writer apparatus, an on/off operation of a well-known load switch is performed for load connected to an antenna circuit included in the data carrier, in accordance with the contents of a response signal to be returned, and thereby, the response is returned. In this way, as a frequency for returning a response from the data carrier, the subcarriers of both sidebands of the carrier frequency of the alternating magnetic field provided from the antenna circuit of the reader/writer apparatus are used.
The data carrier is configured to be provided with a storage section for storing information and an antenna for contactlessly transmitting or transmitting/receiving information in order to contactlessly transmit and receive to and from the reader/writer apparatus with the use of a magnetic field or a radio wave. The data carrier is given various names such as RFID, IC tag, ID tag, RF tag, wireless tag, electronic tag and transponder, and is used in various fields.
As an application example of the data carrier system as described above, it is common that a data carrier is provided for a vending machine, a game machine, an electricity meter, a gas meter, a water meter, a domestic appliance, OA equipment, production equipment and the like, and information about the electronic equipment, such as operation history, sales recording and an amount of use, is stored in the storage section of the data carrier.
Since the data carrier is used in various fields, the form of usage varies accordingly. Among the various usage forms, there is proposed a “complex data carrier” capable of selectively performing both of RF communication and contact serial communication with a reader/writer apparatus (for example, see Patent Document 1).
The “complex data carrier” described in Patent Document 1 is configured as shown in FIG. 11. In FIG. 11, reference numeral 51 denotes a contact point terminal section, reference numeral 52 denotes an antenna coil section, reference numeral 53 denotes a direct current voltage generation section, reference numeral 54 denotes a signal conversion section, reference numeral 55 denotes a signal opening/closing section, reference numeral 56 denotes a first row of signal lines, reference numeral 57 denotes a second row of signal lines, and reference numeral 58 denotes a third row of signal lines.
The contact point terminal section 51 has six terminals: an I/O control terminal, an R/W control terminal, a data (serial) terminal, a write enable terminal, a V+ (power supply) terminal and a GND (ground) terminal. These first five terminals of the contact point terminal section 51 are connected to an MPU 59 and the like constituting an IC section, via the third row of signal lines 58.
The contact point terminal section 51 is a contact terminal section for exchanging data and receiving energy. A GND terminal within a contact terminal for receiving energy is electrically connected to a GND terminal in an integrated circuit for the complex data carrier via a GND connection line. The integrated circuit for the complex data carrier is configured by the direct current voltage generation section 53, the signal conversion section 54 and the signal opening/closing section 55.
Two lead wires of the antenna coil section 52 are connected to the direct current voltage generation section 53 and the signal conversion section 54 in parallel. The antenna coil section 52 is a non-contact terminal section for exchanging data and receiving energy. Though the antenna coil section 52 is used both for exchanging data and receiving energy, data exchange and energy receiving are separated in the frequency domain and/or in the time domain. In the case of separation in the frequency domain, data exchange is performed via a high-pass filter (not shown), and energy receiving is performed via a low-pass filter (not shown). In the case of separation the time domain, connection is switched, for example, by a switching circuit (not shown).
The direct current voltage generation section 53 converts alternating current voltage induced in the antenna coil section 52 to direct current voltage. The direct current voltage obtained by this conversion is used for opening/closing control of the signal opening/closing section 55. To the SE (select enable) terminal of the signal opening/closing section 55, the direct current voltage (V′+) is outputted.
The direct current voltage obtained by this conversion is also power supply for receiving energy. The direct current voltage (V′+) generated by the direct current voltage generation section 53 is supplied to the signal opening/closing section 55, the signal conversion section 54, and the like. That is, power is supplied to the integrated circuit for the complex data carrier. In the case of contactlessly causing an IC card to operate not with the use of the contact point terminal section 51 but with the use of the antenna coil section 52, power is also supplied to the MPU and the like of the IC card via a diode D. Sufficient power is supplied to the antenna coil section 52, and the direct current voltage generation section 53 has a function of stabilizing the direct current voltage to a predetermined voltage value in the use of an ordinary IC card.
The signal conversion section 54 performs demodulation of a signal from the MPU or the like and/or modulation of a signal to the MPU or the like. To the SG (signal) terminal of the signal conversion section 54, the two lead wires of the antenna coil section 52 are connected. A signal demodulated by the signal conversion section 54 is outputted to the first row of signal lines 56. A signal to be modulated by the signal conversion section 54 is inputted from the first row of signal lines 56.
When the direct current voltage of the direct current voltage generation section 53 is predetermined voltage, the signal opening/closing section 55 electrically connects the first row of signal lines 56 and the second row of signal lines 57 with each other, and otherwise, it electrically disconnects them. The signal opening/closing section 55 performs the operation of electrically connecting them or the operation of disconnecting them depending on the direct current voltage inputted to the SE terminal.
Each section of the complex data carrier as described above operates by the voltage applied in a contact state or the voltage applied in a non-contact state. FIG. 12 shows a main part constituting a circuit for controlling rectified voltage VDH which is the main power supply of the analog section, in a power supply control section 124 provided for an RF analog section 120. In FIG. 12, reference numeral 1241 denotes a reference voltage generation circuit; reference numeral 1242 denotes a comparator; reference numeral 1243 denotes a Vcc level detection/set & reset circuit; and reference numeral 1244 denotes a transistor circuit for switch.
The reference voltage generation circuit 1241 outputs reference voltage Vref of a constant value (for example, 2.5 V) irrespective of the level of the rectified voltage VDH of the analog section. The Vcc level detection/set & reset circuit 1243 measures a VDD level, and causes the complex data carrier to be in an operating state (set state) if the magnitude of the VDD voltage applied to the VDD terminal is a predetermined value or higher. If the magnitude is the predetermined value or lower, it causes the complex data carrier to be in a non-operating state (reset state)
The comparator 1242 is a circuit for comparing the reference voltage Vref and the power supply voltage VDD. If the result of comparison is VDD≧Vref, then the transistor circuit for switch 1244 performs an off-operation, and as shown by arrow in FIG. 12, the state of the rectified voltage VDH to the VDD becomes an on-state. If the result of comparison by the comparator 1242 is VDD≦Vref, then the power supply control section 124 is in an on-state.
Patent Document 1: Japanese Patent Application Laid-Open No. 2000-276566
In the data carrier capable of performing both RF communication and contact serial communication as described above, the contact point terminal section 51 is provided with six terminals of an I/O control terminal, an R/W control terminal, a data (serial) terminal, a write enable terminal, a V+ (power supply) terminal and a GND (ground) terminal to realize direct communication.
The cost for forming terminals required for performing contact communication increases in proportion to the number of terminals to be formed. Furthermore, when contact communication is performed, the risk of occurrence of contact failure increases in proportion to the number of terminals. Therefore, it is desirable that the number of terminals formed in a data carrier is as small as possible.